JPS6159007B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a crystal or other piezoelectric vibrator that suppresses high-order vibrations. As is well known, piezoelectric vibrators have many higher-order vibrations in addition to the primary vibration (fundamental vibration) that they are intended to utilize. When an oscillation circuit is constructed using such a piezoelectric vibrator, the oscillation circuit often operates with unnecessary high-order vibrations. Therefore, in order to prevent such high-order vibrations, conventionally, the electrode dimensions of the vibrating piece constituting the piezoelectric vibrator are selected to appropriate values, so that the charges generated with the same polarity can be prevented from causing high-order vibrations. If only the CI of higher-order oscillations is canceled out,
(crystal impedance) value was made larger than that of primary vibration. However, with this method, if there is even a slight manufacturing error in the electrode dimensions, the charge cancellation effect will not be sufficient.
There were drawbacks such as the CI value of the primary vibration being larger than that without charge cancellation.

The purpose of the present invention is to propose a crystal or other piezoelectric vibrator in which prevention of high-order vibrations is achieved by means fundamentally different from charge cancellation. By closely coupling the natural vibration existing in the cage that makes up the piezoelectric vibrator and the higher-order vibration existing in the vibrating element, and reducing the Q value for the higher-order vibration of the piezoelectric vibrator. , to increase the CI value of higher-order vibrations.

Hereinafter, a case will be described in which the present invention is applied to a tuning fork type crystal resonator. FIG. 1 shows an embodiment of the present invention, in which 1 indicates a tuning fork-shaped vibrating piece made of crystal;
It is assumed that the holder is made up of a support member 2 for the vibrating element, an airtight terminal 3, and a sealed tube 4. The problem with the high-order vibrations of the tuning fork type vibrator is mainly the secondary vibration, and the vibration of the tuning fork type vibrating piece is transmitted to the cage in a very small amount. FIG. 2 shows the vibrator shown in FIG. 1 with the sealed tube removed. Second
When the frequency response of the vibrator shown in the figure is measured in a vacuum, the result is as shown in FIG. 3. The horizontal axis in FIG. 3 is the frequency of the driving voltage when the vibrator is driven with a constant voltage (50 mV), and the vertical axis is the value of the current flowing through the vibrator. From Figure 3, the primary vibration of the vibrator is at approximately 32kHz, and the secondary vibration that we are trying to suppress is approximately
The frequency is 185kHz, and the strength of the response (current value of the vibrator) is almost the same as that of the primary vibration. At this time, the CI value of the primary vibration is approximately 180KΩ, and that of the secondary vibration is approximately 20KΩ. In addition, in Figure 2,
The dimensions of the tuning fork type vibrating piece 1 are 6.7 mm in length and 1.4 mm in width.
mm, thickness 0.5mm, slit length 3.7mm, and slit width 0.2mm. By the way, in the vibrator shown in Fig. 1, the sealed tube 4 is made of brass and has a diameter of 3 mm.
If it is designed to have a length of 10 mm and a wall thickness of 0.15 mm, and the airtight terminal 3 is made of Kovar and glass, and the support member 2 is made of Kovar, one of the many natural frequencies that exist in the cage will be a tuning fork type vibration. When the frequency response of the vibrator in Figure 1 (driving voltage 50 mV) is measured, it becomes almost equal to the secondary frequency of piece 1 (the dimensions of the vibrating element are the same as in Figure 2). As shown in , the primary vibration response is at 32KHz,
The strength of the response is almost the same as when there is no sealed tube (Figure 3), but the secondary vibration response has two frequencies slightly apart (184KHz, 186KHz).
The strength of the response is drastically reduced compared to the case without the sealed tube. In this case, the CI value for the two higher-order vibrations becomes a very large value, numerically about 200KΩ. Therefore, suppression of higher-order vibrations has been sufficiently achieved. On the other hand, if the natural frequency of the cage does not nearly match the secondary frequency of the tuning fork vibrating piece, the frequency response will be almost the same as without the sealed tube (Figure 3), or the frequency response will be 185KHz. In addition, a small response appears at around 195KHz. In any case, the strength of the secondary vibration (185KHz) response does not decrease.

As explained above, according to the present invention, the CI value of higher-order vibrations can be made about 10 times larger than that of primary vibrations, so when a vibrator is connected to an oscillation circuit, oscillation of high-order vibrations can be reliably prevented. In addition, the electrode dimensions of the vibrating element can be determined in such a way that the CI value of the primary vibration takes the optimum value.
The effects of the present invention are extremely large. It goes without saying that if the present invention is used in combination with the conventional charge cancellation method, higher-order vibrations can be prevented even further.

Note that the present invention is not limited to tuning fork type crystal resonators, and similar effects are expected for other types of resonators.

[Brief explanation of the drawing]

FIG. 1 is a side view showing a tuning fork type crystal resonator according to an embodiment of the present invention, and FIG. 2 is a side view showing the resonator shown in FIG. 1 with the sealing tube removed.
FIG. 3 is a characteristic diagram showing the frequency response of the vibrator shown in FIG. 2 in vacuum, and FIG. 4 is a characteristic diagram showing the frequency response of the vibrator of the present invention. 1... Tuning fork type crystal vibrating piece, 2... Supporting member, 3
...Hermetic terminal, 4...Sealed tube.

Claims (1)

[Claims] 1. In a piezoelectric vibrator consisting of a piezoelectric vibrating piece and a holder consisting of a support member for the vibrating piece, an airtight terminal, and a sealed tube, the natural frequency of the holder almost matches the higher-order natural frequency of the piezoelectric vibrating piece. A piezoelectric vibrator characterized by: